The first theme is the same one used by Villa-Lobos in his 1925 Choros no. 3 "Pica-pau":
This theme is a drinking song of the Parecis Indians. It was rare for Villa-Lobos to quote an actual Indian song.
This is a real coincidence; I've just been reading Gerard Béhague's article "Indianism in Latin American Art-Music Composition of the 1920s to 1940s: Case Studies from Mexico, Peru, and Brazil", Latin American Music Review / Revista de Música Latinoamericana, Vol. 27, No. 1 (Spring - Summer, 2006), pp. 28-37.
Both these works are good examples of the Brazilian modernist tendency to begin to create a new Brazilian music with reference to both native and popular cultures. 1928 was the year that Oswald de Andrade published his famous Manifesto Antropófago (Cannibal Manifesto):
Its argument is that Brazil's history of "cannibalizing" other cultures is its greatest strength, while playing on the modernists' primitivist interest in cannibalism as an alleged tribal rite. Cannibalism becomes a way for Brazil to assert itself against European postcolonial cultural domination.